Black Americans are at greater risk for hypertensive cardiovascular diseases than whites. Attempts to account for this difference have tried to apply the risk factor approach, in which variables such as heredity, obesity, smoking, alcohol intake, and lack of exercise are presumed to relate directly to this difference. It is generally agreed that the reduction of risk factors is the major goal of any program of the prevention of cardiovascular diseases. An increasing body of evidence supports the concept that cardiovascular reactivity is a marker, and probably an important risk factor in the evolution of coronary heart disease. To date, there are no studies which have addressed differences in cardiovascular reactivity to psychologic challenge between blacks and whites. We have demonstrated that cardiovascular reactivity to phpysical stress does differ between groups of helathy black children and white children. The standard challenge of stress testing produced increased values of the measures of cardiovascular reactivity in the black children. The objectives of this study are 1) to elucidate the mechanism(s) of racial differences in children's exercise cardiovascular reactivity; 2) to evaluate sex differences in physical stress reactivity; 3) to evaluate children's cardiovascular reactivity to psychologic stress; 4) to assess the correlation between physical and psychological stressors. Further lines of investigation and clinical applications extend from this work: 1) the assessment of neuroendocrine functions; 2) non-invasive procedure for risk factor assessment as part of a preventive cardiology program; 3) intervention studies fo risk factor modificaion; 4) prospective studies of coronary heart disease in young individuals.